The experiments proposed here are designed to find out how particular abnormalities in visual experience affect visually guided behavior and the properties of cells in the cat's visual cortex and superior colliculus. Kittens will be raised in environments that provide identical pattern experience to both eyes but prevent one eye from receiving normal visual feedback from eye, head or body movements. The hypothesis is that the colliculus, but not the visual cortex, requires normal visual feedback from movement in order to develop normally. Therefore, the prediction is that the deprived eye will be deficient in its ability to drive collicular cells but not in its ability to drive cortical cells. Behaviorally, the deprived eye should be deficient (relative to the normal eye) in its ability to control behavior requiring visual-motor coordination, but not in its ability to control pattern discrimination. In a second series of experiments kittens will be reared so that both eyes receive normal feedback from movement, but one eye sees only a limited range of spatial frequencies while the other eye sees a much wider range. The hypothesis here is that the visual cortex, but not the colliculus, requires experience with a wide range of spatial frequencies for normal development. The prediction is that the eye seeing the restricted range of spatial frequencies should be deficient (relative to the eye seeing the full range of spatial frequencies) in its ability to drive cortical cells, but not in its ability to drive collicular cells. Behaviorally, the deprived eye should be deficient in its ability to control pattern discriminations but not in its ability to control visual orienting.